Battery powered electronic devices have become ubiquitous. Portable computing devices, tablet computers, laptops, all-in-one computers, wearable computing devices, cell phones, smart phones, media phones, storage devices, portable media players, navigation systems, monitors, power supplies, adapters, remote control devices, chargers, and other devices may be battery powered.
Unfortunately, these batteries may not be ideal. Instead of being an ideal voltage source, they may appear to be a voltage source having series and parallel capacitance, series inductance, and series resistance. These stray components may limit the performance of the batteries and therefore the electronic devices being powered by them.
In various circuits, the series impedance of a battery may cause particular problems. Specifically, a battery may provide a current to one or more circuits in a first electronic device. The battery may also provide current to circuits in one or more other electronic devices connected to the first electronic device. The current for these devices may pass through the series impedance.
The current passing through the series impedance may cause a voltage drop. This voltage drop may lower the effective voltage provided by the battery to the circuits in the first and the other electronic devices.
Various electronic circuits may not operate properly at this reduced voltage. That is, errors in data processing, data transmission, data reception, data display, or other function may be compromised by the reduced voltage. The condition where errors may occur due to a decrease in battery voltage may be referred to as a brownout condition.
It may be desirable to avoid or limit these brownout conditions. To do this, it may be desirable to know when a brownout condition may occur and to be able to reduce its damaging effects.
Thus what is needed are circuits, methods, and apparatus that may detect and mitigate these brownout conditions.